The phosphorus and potassium nutrients significantly affected cotton root area. Low K and High PK treatments performed more than low P treatment at 104 DAT for total absorption area (TAA), at 104 and 148 DAT for active absorption area (AAA) while at 120 DAT negative growth was observed, it could be due to the fact that there was no significant increase in root length after 80 – 90 days of emergence (Nayakekorala and Taylor, 1990).Cotton percentage active absorption area ratio (PAAAR) was high with plants treated to high PK and Low P at 83 DAT. Silberbush and Barber (1983) indicated that greater phosphorus (P) and potassium (K) uptake by maize may also result from the greater root growth as root growth is closely related to P and K uptake. However, High PK treated plants produced the greatest cotton root volume (RV) throughout the experimental period except at 104 and 148 DAT. The high PK treated plants significantly supported root volume which indicates that root hairs and lateral root hairs assist in acquisition of nutrients such as P and K by exploring a greater soil volume and by increasing the absorptive surface of the root (Hallmark and Barber 1984; Jose et al., 2002). Specific surface area (SSA) was significantly affected by nutrients solution. Low P treatment gave highest specific surface area at 83 and 91 days after transplanting. At 104 DAT Low K gave highest specific surface area. At 120 DAT, low K and high PK produced larger specific surface area than Low P. The treatments appeared similar at 148 DAT. Low P and K gave high specific surface area this could be as a result of direct root contact with nutrients solution in hydroponic nutrients solution.